76-13-09\tTELEDYNE CONTINENTAL MOTORS: Amendment 39-2655 as amended by Amendment 39- 2691. Applies to Teledyne Continental Motors Model TSIO-520-L, serial numbers 508000 through 508164, and serial numbers 508166 through 508261. \n\tCompliance required within the next ten hours time in service after the effective date of this AD, unless already accomplished. Inspections covered in steps 1, 2, 3 and 4 below must be repeated each 25 hours time in service from the initial inspection until replaced by a new elbow TCM Part Number 642067 and new exhaust flange TCM Part Number 642066. \n\tTo detect cracks in the left hand rear exhaust elbow, P/N 640708, and the left and right hand flanges on the exhaust to turbo adapter, P/N 640712, and to provide sufficient end clearance between the connector tube assembly, P/N 640711, and the connector tube, P/N 640710, inspect, repair or replace, as required, in accordance with the following procedure: \n\t1.\tRemove couplings, P/N 641284, from each side of the adapter. \n\t2.\tRemove the left hand elbow, (2-4-6 side), P/N 640708, and carefully inspect in the area of the weld closest to the flange, and the flange fillet radius (see illustration for cracks). \n\t3.\tCheck elbow (2-4-6 side), P/N 640708, for distortion in the area shown below (see illustration). \n\n\n\t4.\tIf any cracks are evident and/or distortion is readily discernible, replace the elbow (2-4-6), P/N 640708. (Replace with new elbow 642067 and flange 642066 when parts become available.) \n\t5.\tSlip the connector, P/N 640711, to the right on the elbow (1-3-5 side), P/N 640710, until it bottoms out. With the flanges aligned, the gap between the flange on the turbo adapter (P/N 640712) and the flange on the connector (P/N 640711) must exceed .250 inches but not exceed .500 inches all the way around as shown in illustration. If this gap is less than .250 inches, remove sufficient material from the end of the elbow (1-3-5 side), P/N 640710, to provide .250 to .380 inch gap. If thegap exceeds .500 inches, replace the elbow (1-3-5 side), P/N 640710, with one meeting this inspection requirement. \n\t6.\tRemove the turbo adapter, P/N 640712, from the engine. Carefully inspect the turbo adapter, P/N 640712, for cracks in the flange fillet radii (see illustration). If cracks are observed, replace. \n\t7.\tUsing suitable micrometers or dial indicator calipers, inspect the turbo adapter, P/N 640712, wall thickness in the machined area adjacent to the flange fillet radius on the entire circumference. The minimum allowable thickness is .075 inches (see illustration). If the wall thickness is less than .075 inches in any local area, replace the turbo adapter, P/N 640712, with one meeting this inspection requirement. \n\t8.\tReinstall couplings, P/N 641284. Insure flanges are symmetrically aligned. Tighten couplings to approximately 42 in. lbs. torque. Tap outer periphery of band to distribute tension, then tighten to 50 to 60 in. lbs. of torque. \n\tTCM Service Bulletin M76-14 covers this subject. \n\tAmendment 39-2655 became effective July 15, 1976. \n\tThis amendment 39-2691 becomes effective August 26, 1976.